Concentration of ores by flotation



June 25, 1935.

C. H. KELLER CONCENTRATION OF ORES BY FLOTATION Filed July 27, 1952 .9 Car/red Bottle INVENTOR ATTORNEY-S Patented June 25, 1935 PATENT OFFICE CONCENTRATION OF ORES BY FLOTATION Cornelius H. Keller, San Francisco, Calif., as-

signor to Minerals Separation North American Corporation, New York, N. Y., a corporation of Maryland Application July 27, 1932, Serial No. 624,965

7 Claims.

This invention relates to the concentration of ores by flotation, and is herein illustrated as applied to a variety of ores.

According tothe form of the present invention disclosed in detail, pulps ofthe ores are treated with small amounts of free sulphur-containing acids, such as xanthic acids, and the usual flotation agents, with the result that recovery is enhanced, or a richer concentrate is obtained, or both of these results are achieved.

To achieve these results it is important to follow the correct methods of introducing the free xanthic or other acids.

According to one method the free xanthic acid wasv made by dissolving a sodium or potassium xanthate in water and adding its equivalent amount of a stronger acid, usually sulphuric, in diluted form, immediately before addition to the agitated pulp.

According to a second method the fresh xanthic acid was introduced by producing it in an em closed vessel below the pulp level in the flotation machine and discharging the xanthic acid immediately into the surrounding pulp. This procedure was deemed of especial value because the conspicuous odor of these unstable xanthic acids indicated a, sensible loss if ordinary methods of introduction were employed. For this, and other reasons, extraordinary precautions had to be employed to obtain the best results.

According to a third method, the free acid was made by dissolving or suspending a sodium or potassium xanthate in the corresponding alcohol, and an equivalent proportion of acid, usually sulphuric acid, was introduced, and the resulting alcoholic material added immediately to the agitated pulp, either in the flotation machine or at the grinding mill, as required.

It has been found that good results may be obtained in acid as well as in alkaline circuits by such methods of introducing sulphur-containing acids to the pulp.

In some instances xanthic acids carrying more than three carbon atoms in their molecule, have proved especially useful, as, for example, the xanthic acids made from the higher aliphatic alcohols, such as butyl or amyl, or the cyclic alcohols, such as benzyl or cyclohexanyl.

In the accompanying drawing, Figure 1 is a section through a flotation machine showing one method of introducing the reagent.

Figure 2 is a diagram showing how various proportions of one of the reagents varies the results in concentrating one typical ore.

Nevada Consolidated Copper ore was wet ground with five pounds of calcium oxide per ton, diluted with added water and agitated with 0.1 pound of pine oil, and 0.0075 pound of potassium ethyl xanthate converted to ethyl xanthic acid, all per ton of ore. The xanthic acid was produced by reacting on an aqueous solution of the potassium xanthate with an equivalent proportion of sulphuric acid, producing about three-fourths as much xanthic acidas xanthate, and adding the xanthic acid immediately to the agitated ore pulp below the surface. The pulp was then agitated two minutes and a froth concentrate separated for five minutes.

The concentrate was 4.95% of the weight of the heads. The heads contained 1.33% of copper, the concentrate contained 25.32% copper, and the tailings 0.08% copper, representing a recovery of 94.3%. The recovery and grade were both greater than were obtained when potassium ethyl xanthate was used, as such.

The fresh xanthic acid was advantageously introduced into the orepulp by immersing in the pulp in the spitzkasten l of the flotation machine 2 a glass bottle 3 carrying an aqueous solution of the potassium salt of the desired xanthic acid. The desired acid was produced by pouring the theoretical equivalent of sulphuric acid into a thistle tube 4 passing through the rubber stopper 5 to almost the bottom of the bottle 3. The acid was immediately followed by wash water in sufllcient quantity to wash the acid out into the pulp through a bent tube 6 just passing through he cork 5 and bent horizontally so as to flow the xanthic acid horizontally into the pulp which was in the meantime agitated by the usual propeller 1 at the bottom of the agitation box 8.

A series of parallel tests on the same ore with varying amounts of ethyl xanthic acidused under parallel conditions yielded the results tabu- These results, plotting richness of concentrate and recovery against the amount of xanthic acid used, as shown in the curves of Fig. 2, indicate that the maximum richness of concentrate for this ore was attained at about 0.0038 pounds of xanthic acid per ton, with the aid of other flotation agents.

When amyl, and secondary butyl xanthic acids were substituted for ethyl xanthic acid in the treatment of Nevada Consolidated ore, other conditions remaining the same, equally good results were obtained; in fact the concentrates were slightly richer when using the amount of xanthic acid formed by acidifying 0.0075 pounds per ton of the corresponding potassium xanthates.

It was found that slightly better recoveries or richer concentrates were obtained with ethyl and amyl xanthicacids when the acid was made by acidifying the corresponding xanthate with sulphuric rather than acetic acid, although a butyl xanthic acid prepared with acetic acid was more efficient than one prepared with sulphuric acid.

Fresh furfuryl xanthic acid prepared by adding acetic acid to an aqueous solution of potassium furfuryl xanthate was used in concentrating Nevada Consolidated as follows v The ore was reground for 7 minutes from 10- mesh with 5 pounds of calcium oxide per ton, made into a pulp with added water and agitated with 0.1 pound of pine oil and a calculated 0.05 pound of the fresh furfuryl xanthic acid. The pulp was then agitated two minutes and a froth concentrate separated for five minutes.

The concentrate was 5.63% of the weight of the heads. The heads contained 1.36% copper, the concentrate 22.56%, and the tailing 0.1% of copper, representing a recovery of 93.1%.

Fresh furfuryl xanthic acid prepared by adding sulphuric acid to an aqueous solution of potassium furfuryl xanthate, in a parallel test, yielded the following results:

The concentrates were 5.12% the weight of the heads. The heads contained 1.36% copper, the concentrate 24.64% and the tailings 0.11% of copper, representing a recovery of 92.4%.

Nevada Consolidated Copper ore was ground with five pounds of calcium oxide, per ton, made intora pulp with added water and. agitated with 0.1 pound of pine oil and with freshly made benzyl xanthic acid, made by acidifying with dilute sulphuric acid 0.005 pound of potassium benzyl xanthate, all per ton of ore. The .pulp was agitated for two minutes and then a froth concentrate separated for six minutes. The concentrate was 4.71% of the weight of the heads. The heads contained 1.376% copper, the concentrate 23.76%, and the tailings 0.27% copper, representing a recovery of 81.3%.

When 0.01 pound of the postassium benzyl xanthate were substituted for the 0.005 pound in a parallel test with heads containing 1.364% copper, a concentrate was obtained equal to 4.91% of the heads. The concentrate contained 25.44% copper, and the tailings 0.12% copper representing a recovery of 91.6%.

Nevada Consolidated Copper ore was ground with five pounds of calcium oxide, per ton, made into a pulp with added water and agitated with 0.1 pound of pine oil and with freshly made cyclohexanol xanthic acid made by acidifying with dilute sulphuric acid 0.005 pound of potassium cyclohexanol xanthate, all per ton of ore. The pulp was agitated for two minutes and then a froth concentrate separated for six minutes. The concentrate was 4.73% of the weight of the heads. The heads contained 1.359% copper, the concentrate 24.32% and the tailings 0.22% copper, representing a recovery of 84.6%

When 0.01 pound of the potassium cyclohexanol xanthate was substituted for the 0.005 pound in a parallel test with heads containing 1.363% copper, a concentrate was obtained equal to 4.23% of the heads. The concentrate contained 26.64% copper, and the tailings 0.11% copper, representing a recovery of 92.3%.

When Clay Mine ore of Phelps Dodge Corporation was wet ground with 5 pounds calcium oxide, diluted with water and agitated with 0.15 pound of pine oil and 0.05 pound of cresylic acid, and with fresh xanthic acid made by adding sulphuric acid to 0.02 pound of potassium ethyl xanthate, all per ton of ore, the following results were obtained by agitating two minutes and separating froth for'ten minutes.

The concentrates were 11.1% of the weight of the heads. The heads contained 0.87% of copper, the concentrate 6.96% copper, the tails 0.11% copper, representing a recovery of 88.8%. This may be compared with a concentrate containing 6.48% copper and a tailing of 0.13% copper when the corresponding amount of potassium xanthate was substituted for the xanthic acid.

When Miami Copper Company ore was wet ground with 3 pounds of calcium oxide, diluted with added water, and agitated with 0.1 pound of pine oil and with fresh xanthic acid made by adding sulphuric acid to 0.0075 pound of potassium ethyl xanthate, all per ton of ore, the following results were obtained by agitating two minutes and separating froth for five minutes.

The concentrates were 4.1% of the weight of the heads. The heads contained 0.72% copper, the concentrate 14%, and the tailings 0.15% copper, representing a recovery of The richest concentrate obtained when potassium xanthate was used was just over 11% copper.

When less xanthic acid was used, equivalent to 0.005 pound per ton of potassium ethyl xanthate, a conventrate was obtained containing 14.96 of copper, with a recovery of 78.7%.

.Ethyl xanthic acid, amyl xanthic acid, butyl xanthic acid, all proved useful in connection with Morenci ore of Phelps-Dodge Corporation.

When the Morenci ore was wet ground with 5 pounds calcium oxide, with added water and agitated with 0.1 pound of pine oil and with fresh ethyl xanthic acid made by adding sulphuric acid to 0.05 pound of potassium ethyl xanthate, all per ton of ore, the following results were obtained:

The concentrates were 10.7% of the weight of the heads. The heads contained 1.69% copper, the concentrate 14.08%, and the tailings 0.20% copper, representing a recovery of 89.4%.

A richer concentrate with a lower recovery was obtained when 0.01 pound of potassium ethyl xanthate was used for producing the xanthic acid instead of the 0.05 pound just described.

When another lot. of the same Morenci ore was similarly concentrated, using 0.025 pound of potassium amyl xanthate, so as to yield amyl 'per ton. of ore.

tassium butyl xanthate, so as to yield butyl xanthic acid, the results were as follows:

The concentrates were 11% of the weight of the heads. The heads contained 1.77% copper, the concentrate 14.32% and the tailings 0.22% copper, representing a recovery of 84.8%.

When another lot of the same Morenci ore was similarly concentrated, substituting 005 pound of potassium furfuryl xanthate for the ethyl xanthate, the results were as follows:

The concentrates were 9.3% of the weight of the heads. The heads contained 1.74% ofcopper, the concentrate 16.16%, and the tailings 0.26%, representing a recovery of 86.4%.

Parallel improvement in concentration was obtained when other acids than xanthic acids were introduced into ore 'pulps.

Nevada Consolidated Copper ore was ground with five pounds of calcium oxide, per ton, made into a pulp with added water and agitated with 0.1 pound of pine oil and with freshly made dibutyldithiophosphoric acid, made by acidifying with dilute sulphuric acid 0.02 pound of the commercial compound known as #208 aerofloat, all The pulp was agitated for two minutes and then a froth concentrate separated for five minutes.

The concentrate was 4.62% of the weight of the heads. 2 The heads contained 1.41% copper, the concentrate 27.20%, and the tailings'0.16% copper, representing a recovery of 89.2%.

The 27.2% copper in the concentrate compared favorably with the best, 25.28% of copper obtained by parallel test procedures in which the sodium salt, #208 aerofloat, was used instead of the acid, and the recovery was greater, with the same proportion of copper. in the tailing in both tests. r j

When another lot of the same Nevada Consolidated ore was similarly concentrated, substituting 0.006 pound of the #208 aerofloat forthe 0.02

pound, to make dibutyldithiophosphoric acid, the results were as follows:

The concentrate was 4.84% of the weight of the heads. The heads contained 1.34% of copper,-

the concentrate 25.04%, and the tailings 0.13% copper, representing a recovery of 90.7%.

An even better grade of concentrate, 25.84%, was obtained when concentration. was effected with the aid of 0.004% of the #208 aerofloat converted to the acid, though the recovery was less, viz., 86.2%.

When ,the same ore was concentrated by the aid of diethyldithiophosphoric acid made by treating commercial sodium aerofloat with dilute sulphuric acid, the concentrate was usually richer or the tailings carried less copper than when the ore was concentrated-with a corresponding amount of the'unchanged sodium aerofioat.

When a fresh sample of Utah Copper Company ore was concentrated by grinding with 6 pounds of calcium oxide and 0.25 pound sodium cyanide,

' both per ton, diluted with added water, and agitated with 0.4 pound cresylic acid and diethyldithiophosphoric acid madeby treating 0.04 pound sodium aerofloat with dilute sulphuric acid, both perton, the following result was obtained:

The concentrate was 5.55% of the weight of the heads. The heads contained 0.97% copper, the concentrate 13.44% and the tailings 0.24% copper, representing a recovery of 77.8%. This compared with a. parallel test of the same ore, substituting the sodium aerofloat for the diethyldithiophosphoric acid, in which heads carrying 0.95% copper yielded a concentrate carrying 11.68% copper and a tailing of 0.23% copper,a slightly poorer recovery and an inferior concentrate.

When the xanthic acid was made by dissolving or suspending a xanthate in the corresponding alcohol and treating with an equimolecular pro portion of acid, an agent was obtained which often proved extraordinarily useful for assisting in the production of rich concentrates or large recoveries in ore concentration. Some of the results are shown in the following examples:

In a series of tests Nevada Consolidated copper ore was reground for 7 minutes from 10-mesh with pounds of calcium oxide per ,ton in a laboratory ball mill, diluted with added water and agitated with 0.05 pound xanthic acid carried in ethyl alcohol and 0.1 pound pine oil, both concentrate 23.84%, andthe tailings 0.07% copper, representing a recovery of 95.1%.

In another test the calculated amount of xanthic acid was prepared by adding hydrochloric acidto amyl alcohol carrying 10% potassium amyl xanthate. The concentrate was 5.43% of the weight of the heads. The heads contained 1.34% of copper, the concentrate 23.44%, and the tailings 0.07% copper, representing a recovery of 95.1%. f

In'another test the calculated amount of xanthic acid was prepared by adding sulphuric acid (in half equimolecular proportion) to butyl alcohol carrying 10% potassium butyl xanthate. The concentrate was 5.52% of the weight of the heads. The heads contained 1.34% copper, the concentrate 23.28% and the tailings 0.06% copper, representinga recovery of 95.7%.

terial was found to increase both the grade of concentrate and the recovery of zinc in the concentration of a zinc ore.

A pulp of Joplin zinc ore was agitated with 1.5 pounds copper sulphate, Barrett #634 0.2 pound, pine oil 0.3 pound, and the acid by adding the theoretical equivalent of sulphuric acid to 0.2 pound potassium furfuryl xanthate, all per ton of ore. After agitating for two minutes a froth concentrate was separated for five minutes.

The results were as follows:

The concentrates were 21.1% of the weight of the heads. The heads contained 14.29% of zinc, the concentrates 62.0%, and the tailings 1.5%, representing a recovery of 91.7%. best results with the corresponding xanthate were a concentrate containing 60.8% zinc with a 1.9%

tailing.

A partially oxidized copper Exploration Company, Antofagasta, Chile, was ground wet in a ball mill, diluted with more water and agitated in a flotation machine. To' this pulp were added 0.15 lb. of cresol per ton of ore, and the xanthic acid corresponding to 0.2 pound ore from the Chile The Copper Recovery Product Weight Total Oxide Total Cu Oxide Cu 7 Percent Percent Percent Percent Percent Heads 100. 00 2. 35 0. 64 100. 0 100. 0 1st concentrate. 8. 70 15.20 1. 92 56. l .2 2nd concentrate.-. 6. 77 13. 52 5. 96 38. 9 63. 2 Taih'ngs 84. 53 0. 14 0. 08 5. 0 10. 6

Amyl xanthic acid was used in concentrating a v lead ore as follows:

A pulp of Deslodge Lead Company ore was agitated with 0.1 pound pine oil and amyl xanthic acid made by adding the theoretical equivalent of dilute sulphuric acid to an aqueous solution carrying 0.05 pound per ton of potassium amyl Xanthate, and a froth concentrate separated. The xanthate solution was mixed with the .acid immediately before adding to the agitated pulp.

The results 'were as follows:

The concentrates were 8.93% of the weight of the heads, the heads contained 4.65% of lead, the concentrates 50% and the tailings 0.2% of lead, representing a recovery of 96.1%. 1

Morning Mine lead-zinc orewas concentrated by wet grinding for 20 minutes with 0.2 pound sodium cyanide and 1 pound zinc sulphate, both per ton of ore, diluting with added water, and agitating the pulp with 0.2 pound cresylic acid to yield a lead float. The remaining pulp was agitated with 1 pound copper sulphate, 0.2 pound Barrett #4, and 0.05 pound pine oil, all per ton of-ore, to yield a zinc float. In addition to the foregoing there was added, at the beginning of the agitation, amyl xanthic acid made by adding the theoretical equivalent of sulphuric acid to 0.025 pound potassium amyl xanthate, per ton. of the ore.

The weight of the lead concentrate was 17% of the heads and of the zinc concentrate 9.0% of the heads. The heads contained 9.26% lead and 5.9% zinc. The lead concentrate contained 52.6 lead, and the zinc concentrate 40.2% zinc. The tailings contained 0.1% of lead and 0.3% of zinc, representing a recovery of 96.7 of lead and 61.5% zinc in their respective concentrates.

A pulp of Mexican Candelaria silver ore was agitated with 0.1 pound pine oil and amyl xanthic pound Yarmor pine oil, and fresh amyl xanthic acid made by acidifying with sulphuric acid 0.4 pound potassium amyl xanthate, all per ton of ore, and a rougher froth concentrate separated. The rougher concentrate thus obtained wasretreated to yield a finished concentrate and a middling. The results are shown in the following table:

Weight Au Recoverlw Percent Ounces Percent Heads 100. 0 0. 289 100.

When 'the potassium amyl xanthate was replaced by potassium butyl xanthate to yield the corresponding xanthic acid in a parallel test, the following results were obtained:

Weight Au Recoveries Ounces Percent Having thus described certain embodiments of the invention, what is claimed is:

1. The process of concentrating an ore which consists in dispersing in an alkaline ore pulp, an appreciable amount of separately prepared free xanthic acid but in a proportion of less than 0.05 pound per ton of solids in the pulp, agitating such pulp with a further agent such as will produce a floating concentrate, and separating the float.

2. The process of concentrating an ore which consists in dispersing in an alkaline ore pulp free xanthic acid carrying more than three atoms of carbon in the molecule, agitating such pulp with a further agent such as will produce a float.- ing concentrate, and separating the float.

3. The process of concentrating an ore which consists in dispersing in an alkaline ore pulp free xanthic acid made from an aliphatic alcohol and carrying more than three atoms of carbon in the molecule, agitating such pulp with a further agent such as will produce a floating.concentrate, and separating the float.

4. The process of concentrating an ore which consists in dispersing in an ore pulp free xanthic acid made from a cyclic alcohol, agitating such pulp with a further agent such as will produce a floating concentrate, and separating the float.

5. The process of concentrating an ore which consists in dispersing in an ore pulp free furfuryl xanthic acid, agitating such pulp with a further agent such as will produce a floating concentrate, and separating the float.

6. The process of concentrating an ore which consists in dispersing in an alkaline ore pulp free furfuryl xanthic acid, agitating such pulp with a further agent such as will produce a floating concentrate, and separating the float.

'7. The process of concentrating an ore which consists in dispersing in an ore pulp alcohol garrying a freshly prepared free xanthic acid, agitating with such other agent as will produce a floating concentrate, and separating the float.

CORNELIUS H. KELLER. 

